Background: Differentiating cardiogenic versus noncardiogenic causes of respiratory signs can be challenging when echocardiography is unavailable. Radiographic vertebral left atrial size (VLAS) and vertebral heart size (VHS) have been shown to predict echocardiographic left heart size, with VLAS specifically estimating left atrial size. Hypothesis/objectives: Compare the diagnostic accuracy of VLAS and VHS to predict 12left-sided congestive heart failure (CHF) in dogs presenting with respiratory signs. Animals: One-hundred and fourteen dogs with respiratory signs and radiographic pulmonary abnormalities. Methods: Retrospective cross-sectional study. Dogs had to have an echocardiogram and thoracic radiographs obtained within 24-hours. Diagnosis of CHF was confirmed based on the presence of respiratory signs, cardiac disease, LA enlargement, and cardiogenic pulmonary edema. Results: Fifty-seven dogs had CHF-yes and 57 had CHF-no. Compared to VHS (area under the curve [AUC] 0.85, 95% CI 0.77-0.91), VLAS was a significantly (P=0.03) more accurate predictor of CHF (AUC, 0.92, 95% CI 0.85-0.96). Optimal cutoff for VLAS was >2.3 vertebrae (sensitivity 93.0%, specificity 82.5%). Compared to murmur grade (P=0.40) and VHS (P=0.11), only VLAS (P<0.0001) was independently associated with CHF. Increased VHS (54%) was significantly (P=0.007) more common than increased VLAS (24%) in dogs with CHF-no. Results were similar in a subpopulation of older and smaller dogs.
